std::queue<T,Container>::emplace

Since C++17

Pushes a new element to the end of the queue. The element is constructed in-place, i.e. no copy or move operations are performed. The constructor of the element is called with exactly the same arguments as supplied to the function.

# Declarations

template< class... Args >
void emplace( Args&&... args );

(since C++11) (until C++17)

template< class... Args >
decltype(auto) emplace( Args&&... args );

(since C++17)

# Parameters

args: arguments to forward to the constructor of the element

# Return value

(none)

# Example

#include <iostream>
#include <queue>
 
struct S
{
    int id;
 
    S(int i, double d, std::string s) : id{i}
    {
        std::cout << "S::S(" << i << ", " << d << ", \"" << s << "\");\n";
    }
};
 
int main()
{
    std::queue<S> queue;
    const S& s = queue.emplace(42, 3.14, "C++"); // for return value C++17 required
    std::cout << "id = " << s.id << '\n';
}

# Defect reports

DR	Applied to	Behavior as published	Correct behavior
LWG 2783	C++17	emplace returned reference, breaking compatibility with pre-C++17 containers	returns decltype(auto)